The action of seven convulsants as antagonists of the GABA response of Limulus neurons

Abstract 1. Intracellular recordings were made from neurons in the abdominal ganglia of Limulus polyphemus . GABA was inhibitory on all the neurons tested. 2. Picrotoxinin was approximately equipotent with picrotoxin as a reversible antagonist of the GABA inhibitory response. 3. Picrotin, the inactive component of picrotoxin, reversibly antagonized the GABA inhibitory response but was 19 times less potent than picrotoxinin. 4. Both t -butylbicyclophosphate and tetramethylenedisulphotetramine reversibly antagonized the GABA inhibitory responses, but were 2410 and 2705 times respectively less potent than picrotoxinin. 5. Bicuculline methochloride and p -tolyl silatrane had no blocking action on the GABA inhibitory responses of these neurons.